• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2011년도 추계학술발표대회
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• pp.1174-1176
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• 2011

Unfortunately, the number of blind people increases every 5 seconds in our world. An extensive research was made on improving the conventional walking cane and developing a microcontroller based walking stick for the blind with sensors and a feedback in form of vibration. Two different kinds of sensors are used to detect obstacles, ultrasonic and infrared distance sensors. The signal from an ultrasonic sensor is fed to a microcontroller. With the help of the supporting software, the Pulse Width Modulation (PWM) principle is extensively used to form three zones and run the corresponding vibration motor at different spends according to how far the detected object is located. The other infrared distance sensors are connected to amplifiers and after that to their corresponding vibration motors through motor drivers. The vibration motors are to be located around the user's arm to notify the blind of the obstacles in the intended walking way. It can be very reliable and sufficient device guiding the blind other than the conventional walking cane which has many drawbacks which will be explained and discussed.

• Journal of the Korea Institute of Information Security & Cryptology
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• 제11권3호
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• pp.33-44
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• 2001

E-commerce has various advantages such as saving the cost and no constraint on time and space, unlike real-world commerce. On the other hand, e-commerce has some important issues to solve since the commerce is conducted on the cyberspace. The issues are a mutual confidence of parties participating in the commerce as well as a method of payments. On early days, electronic cash was designed using blind digital signature to protect the personal information from being exposed and to provide the perfect anonymity for user. In this paper, a new blind signature scheme based on Feige-Fiat-Shamir digital signature is proposed, which is very efficient compared with the other schemes in terms of the computational complexity. Also, a traceable Electronic Cash System which is based on the proposed blind digital signature is designed, which has a nice feature of identifying the spender in case of using the money illegally.

• Journal of rehabilitation welfare engineering & assistive technology
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• 제1권1호
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• pp.7-11
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• 2007

A compass device which indicates the right direction using the recorded voice was developed to assist the people who are blind when they are walking and moving to somewhere. The developed voice compass consists of a sensing module which recognizes the terrestrial magnetism with magnetic sensor, voice recorder IC, speaker and microprocessor which controlled all the components. It has 32 directions resolution and can continuously indicates the progressing direction with established time interval for the user convenience. It can help walking of the blind people and designed to be used in various sports and leisure. The performance of the developed device was verified by experiment with person who are blind.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제24권7A호
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• pp.939-946
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• 1999

A new blind multi-user channel estimation algorithm for the mobile communication systems is proposed. The proposed algorithm exploits the second-order statistics of a received signal and the subspace concept, and requires much less computational complexity than the existing algorithms. The algorithm can reduce the comptational load by estimating the physical channels excluding the spreading codes. We formulate the algorithm using the multi-channel model for asynchronous DS-CDMA systems and perform numerical experiments to evaluate the performance of the proposed algorithm.

• Journal of Communications and Networks
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• 제9권1호
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• pp.28-33
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• 2007

Estimated channel information, especially multipath length and multipath channel of the desired user, is necessary for most previously reported linear blind multiuser detectors in code division multiple access (CDMA) systems. This paper presents a new blind intersymbol decorrelating detector in asynchronous CDMA systems, which uses the cross correlation matrix of the consecutive symbols. The proposed detector is attractive for its simplicity because no channel estimation is required except the synchronization of the desired user. Compared with other reported multiuser detectors, simulation results show that the proposed detector provides a good performance when the active users have significant intersymbol interference and the multipath length is short.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제18권2호
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• pp.33-48
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• 2018

In this paper, we characterise the joint interference alignment and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with a blind interference alignment through staggered antenna switching on the receiver. We explore the power allocation and the feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired and interference signals to cancel the common interference signals, since the received signal must have a corresponding independent signal subspace. The sum capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised.

• Journal of Information Processing Systems
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• 제14권5호
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• pp.1102-1113
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• 2018

Vibrotactile feedback is widely used in designing non-visual interactions on mobile phones, such as message notification, non-visual reading, and blind use. In this work, novel vibrotactile codes are presented to implement a non-visual text reading system for mobile phones. The 26 letters of the English alphabet are formed in an index table with four rows and seven columns, and each letter is mapped using the codes of vibrations. Two kinds of vibrotactile codes are designed with the actuator's on and off states and with specific lengths (short and long) assigned to each state. To improve the efficiency of tactile perception and user satisfaction, three user experiments are conducted. The first experiment explores the maximum number of continuous vibrations and minimum vibration time of the actuator's on and off states that the human can perceive. The second experiment determines the minimum interval between continuous vibrations. The vibrotactile reading system is designed and evaluated in the third experiment according to the results of the two preceding experiments. Results show that the character reading accuracy reaches 91.7% and the character reading speed is approximately 617.8 ms. Our method has better reading efficiency and is easier to learn than the traditional Braille coding method.

• ETRI Journal
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• 제41권4호
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• pp.426-436
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• 2019

In time division duplex (TDD)-based multiuser massive multiple input multiple output (MIMO) systems, the uplink channel is estimated and the results are used in downlink for signal detection. Owing to noisy uplink channel estimation, the downlink channel should also be estimated for accurate signal detection. Therefore, recently, a blind method was developed, which assumes the use of a linear high-power amplifier (HPA) in the base station (BS). In this study, we extend this method to a scenario with a nonlinear HPA in the BS, where the Bussgang decomposition is used for HPA modeling. In the proposed method, the average power of the received signal for each user is a function of channel gain, large-scale fading, and nonlinear distortion variance. Therefore, the channel gain is estimated, which is required for signal detection. The performance of the proposed method is analyzed theoretically. The simulation results show superior performance of the proposed method compared to that of the other methods in the literature.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1586-1589
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• 2002

RLS algorithm is a kind of the adaptive algorithms in smart antennas and adapts the weight vector using the difference between the output signal of array antennas and the known training sequence. In this paper, we propose a new algorithm based on the RLS algorithm. It calculates the error signal with reference signal derived from blind scheme. Simulation results show that the proposed algorithm yields more user capacity by 67∼74% than other blind adaptive algorithms(LS-DRMTA, LS-DRMTCMA) at the same BER and the beamformer forms null beams toward interference signals and the main beam toward desired signal.

• ETRI Journal
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• 제42권1호
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• pp.26-35
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• 2020

Herein, we consider uplink multiuser massive multiple-input multiple-output systems when multiple users transmit information symbols to a base station (BS) by applying simple space-time block coding (STBC). At the BS receiver, two detection filters for each user are used to detect the STBC information symbols. One of these filters is for odd-indexed symbols and the other for even-indexed symbols. Using constrained output variance metric minimization, we first derive a special relation between the closed-form optimal solutions for the two detection filters. Then, using the derived special relation, we propose a new blind adaptive algorithm for implementing the minimum output variance-based optimal filters. In the proposed adaptive algorithm, filter weight vectors are updated only in the region satisfying the special relation. Through a theoretical analysis of the convergence speed and a computer simulation, we demonstrate that the proposed scheme exhibits faster convergence speed and lower steady-state bit error rate than the conventional scheme.